Embodiments of the disclosure permit automated focusing of a camera module during assembly. The camera module can include an imaging device and a lens assembly that is movably mounted to a housing of the camera module. In certain embodiments, the automated focusing can include iteratively imaging a fixed set of reference markings, and successively quantifying the focusing quality of the camera module based at least on a defocus metric defined as a difference between a current spacing and a calibrated spacing among two of the imaged reference markings. The magnitude and sign of the defocus metric can guide, respectively, a magnitude and direction of the movement of the lens assembly relative to the imaging device. After successive adjustments yield a desired focusing quality of the camera module, the lens assembly can be locked in position and can be further processed according to a suitable camera module integration flow.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method, comprising: receiving image data from a red-green-blue (RGB) light sensor included in a camera module, the image data being representative of an image of a test chart having two reference markings; determining a separation distance between the two reference markings in the image; determining a defocus metric for the image, wherein the defocus metric is a difference between the separation distance and a reference separation distance between the two reference markings, and wherein the reference separation distance is a spacing between the two reference markings in a focused image of the test chart obtained by the camera module; determining that a magnitude of the defocus metric is greater than a magnitude of a tolerance parameter; directing a positioning mechanism to move a lens assembly of the camera module by a distance determined by the magnitude of the defocus metric and in a direction determined by a sign of the defocus metric; receiving second image data from the RGB light sensor after the lens assembly is moved, the second image data being representative of a second image of the test chart; determining a second separation distance between the two reference markings in the second image; determining a second defocus metric for the second image as a difference between the second separation distance and the reference separation distance; determining that a second magnitude of the second defocus metric is equal to or less than a second magnitude of the tolerance parameter; and directing the positioning mechanism to maintain a current position of the lens assembly with respect to the RGB light sensor, and the current position is maintained to affix the lens assembly to a housing of the camera module.
2. The method of claim 1 , wherein directing the positioning mechanism to move the lens assembly comprises determining that the defocus metric is a positive number, and directing the positioning mechanism to move the lens assembly, from an initial position, by a predetermined distance towards the RGB light sensor.
3. The method of claim 1 , wherein directing the positioning mechanism to move the lens assembly of the camera module comprises determining that the defocus metric is a negative number, and directing the positioning mechanism to move the lens assembly, from an initial position, by a predetermined distance away from the RGB light sensor.
4. The method of claim 1 , further comprising positioning the lens assembly at an initial distance from the RGB light sensor, the initial distance corresponding to a nominal back focal length of the lens assembly.
5. The method of claim 1 , wherein the RGB light sensor comprises multiple photodetectors, each configured to receive light and to generate an imaging signal in response to the received light, and wherein determining that the magnitude of the defocus metric is greater than the magnitude of the tolerance parameter comprises determining that the magnitude of the defocus metric is greater than a separation distance between a pair of the multiple photo detectors.
6. A control device, comprising: at least one memory device having instructions encoded thereon; and at least one processor coupled to the at least one memory device and configured, by at least a portion of the instructions, to at least: receive image data from an imaging device included in a camera module, the image data being representative of an image including at least two reference markings; determine a spacing between the two reference markings in the image; determine a defocus metric for the image as a difference between the spacing and a reference spacing; and direct a positioning mechanism to adjust the position of a lens assembly of the camera module by a distance determined by a magnitude of the defocus metric in a direction determined by a sign of the defocus metric.
7. The control device of claim 6 , wherein the at least one processor is further configured, by at least the portion of the instructions, to determine that a magnitude of the defocus metric is greater than a predetermined threshold, and to direct the positioning mechanism to move the lens assembly relative to the imaging device by a distance determined by the magnitude of the defocus metric in a direction determined by the sign of the defocus metric.
8. The control device of claim 6 , wherein the at least one processor is further configured, by at least the portion of the instructions, to determine that the defocus metric is a positive number, and to direct the positioning mechanism to move the lens assembly by a predetermined distance towards the imaging device.
9. The control device of claim 6 , wherein the at least one processor is further configured, by at least the portion of the instructions, to determine that the defocus metric is a negative number, and to direct the positioning mechanism to move the lens assembly a predetermined distance away from the imaging device.
10. The control device of claim 6 , wherein the at least one processor is further configured, by at least the portion of the instructions, to determine that a magnitude of the defocus metric is equal to or less than the predetermined threshold, and to direct the positioning mechanism to lock the lens assembly in its current position.
11. The control device of claim 7 , wherein the imaging device includes multiple photosensitive elements, and wherein the at least one processor is further configured, by at least the portion of the instructions, to determine that the magnitude of the defocus metric is greater than a separation between a pair of the multiple photosensitive elements.
12. The control device of claim 6 , wherein the image represents a test chart including a spatial frequency response (SFR) chart.
13. The control device of claim 6 , wherein each of the two reference markings has a predetermined shape, and wherein a first marking of the two reference markings is disposed in the test chart at a predetermined orientation relative to a second marking of the two reference markings, the predetermined orientation being one of a vertical orientation, a horizontal orientation, or an orientation along a direction having an inclination different from zero degrees or 90 degrees.
14. The control device of claim 6 , wherein the at least one processor is further configured, by at least the portion of the instructions, to direct the positioning mechanism to place the lens assembly at an initial distance from the imaging device corresponding to a nominal back focal length of the lens assembly.
15. At least one non-transitory computer-readable storage medium comprising instructions, that when executed, cause a controller to perform operations comprising: receiving image data from an imaging device included in a camera module, the image data being representative of an image including at least two reference markings; determining a spacing between the two reference markings in the image; determining a defocus metric for the image as a difference between the spacing and a reference spacing; and directing a positioning mechanism to adjust the position of a lens assembly of the camera module by a distance determined by a magnitude of the defocus metric in a direction determined by a sign of the defocus metric.
16. The at least one non-transitory computer-readable storage medium of claim 15 , wherein the operations further comprise determining that the magnitude of the defocus metric is greater than a predetermined threshold, and directing the positioning mechanism to move the lens assembly relative to the imaging device by a distance determined by the magnitude of the defocus metric in a direction determined by the sign of the defocus metric.
17. The at least one non-transitory computer-readable storage medium of claim 15 , wherein the operations further comprise determining that the defocus metric is a positive number, and directing the positioning mechanism to move the lens assembly by a predetermined distance towards the imaging device.
18. The at least one non-transitory computer-readable storage medium of claim 15 , wherein the operations further comprise determining that the defocus metric is a negative number, and directing the positioning mechanism to move the lens assembly by a predetermined distance away from the imaging device.
19. The at least one non-transitory computer-readable storage medium of claim 15 , wherein the operations further comprise determining that a magnitude of the defocus metric is equal to or less than the predetermined threshold, and directing the positioning mechanism to lock the lens assembly in its current position.
20. The at least one non-transitory computer-readable storage medium of claim 15 , wherein the operations further comprise directing the positioning mechanism to place the lens assembly at an initial distance from the imaging device corresponding to a nominal back focal length of the lens assembly.
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November 14, 2014
December 6, 2016
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